How does air intake work in Kerbal Space Program?

[BACK]
How does air intake work in Kerbal Space Program?
Posted On: April 3, 2023

I've just started building planes and am confused about the way air intake works. For instance, the J-90 "Goliath" Turbofan Engine is specified to consume a whopping 132.272 Air/sec while supplying Intake Air: 3.4 (presumably this is per second as well?).


How would I supply such an engine, let alone two?


The largest supplier of air that I can find seems to be the Engine Nacelle with Intake Air: 5.0 (similarly the Engine Pre-Cooler that takes in the same amount but is more expensive and lighter). That means, if I want to supply one Goliath, I'd need about 26 Nacelles, or 65 Radial Air Intakes (which claim to provide`Intake Air: 2.0). Presumably this is the maximum intake ASL, which supposedly drops higher in atmo (and probably depends on speed). So this doesn't sound like the correct way to determine air requirements.


So: How do I translate the Intake Air figure I see in the Item description to the usable amount of air/sec that I have available for my engines?


Question from user bitmask at gaming.stackexchange.com.


Answer:

First, differentiate between intake air use/production, and intake air storage. It's a resource similar to electric energy or monopropellant. It's scooped by the intakes, stored in "tanks" provided by the intakes and drawn by engines from these "tanks". And since you're not supposed to be able to take a good supply of intake air to the orbit, the "tanks" provided are of puny size. Engine Nacelle can store 5 units of intake air, but it can scoop much, much more than that per second.


I can't give you a precise answer how to find out the rates, just - don't overthink it and don't worry. In most cases 1 intake (any) per engine is aplenty, 1 per 2 engines is sufficient. The primary practical difference is in aerodynamic properties, that is how much drag it causes - e.g. circular intakes are bad for supersonic flight. .


Thing is, the amount of intake air changes with atmospheric density, and that changes with altitude - exponentially (it also depends on airspeed and the intake area facing "into the wind" so if you mount your intakes backwards - or your plane turns tail-forward - you may face air starvation). At altitudes up to 20km you'll have to fail pretty hard to starve your engine of air. Above that - around 24-26km - there's an altitude threshold at which air becomes too thin and your engines are starved of air. Note the exponential nature of pressure makes the threshold hit hard; you can do very little about shifting it. You may push maybe a kilometer up through use of plenty intakes, but it's not really worth it (the extra drag from the added intakes will contribute more negatively than the extra flight altitude will benefit you).


There's a plenty of other "hidden" characteristics of the jet engine, like airspeed-thrust curve, pressure-thrust curve, etc. Goliaths are, for example, subsonic engines which really lose power at higher speeds, and won't allow for extreme altitudes either. And they have intakes big and efficient enough that it's very hard to starve them of air - you'll run out of thrust long before you reach altitude where their intakes can't keep up with the consumption. .


Answer from user SF. at gaming.stackexchange.com.



[BACK]
How does air intake work in Kerbal Space Program?
Posted On: April 3, 2023

I've just started building planes and am confused about the way air intake works. For instance, the J-90 "Goliath" Turbofan Engine is specified to consume a whopping 132.272 Air/sec while supplying Intake Air: 3.4 (presumably this is per second as well?).


How would I supply such an engine, let alone two?


The largest supplier of air that I can find seems to be the Engine Nacelle with Intake Air: 5.0 (similarly the Engine Pre-Cooler that takes in the same amount but is more expensive and lighter). That means, if I want to supply one Goliath, I'd need about 26 Nacelles, or 65 Radial Air Intakes (which claim to provide`Intake Air: 2.0). Presumably this is the maximum intake ASL, which supposedly drops higher in atmo (and probably depends on speed). So this doesn't sound like the correct way to determine air requirements.


So: How do I translate the Intake Air figure I see in the Item description to the usable amount of air/sec that I have available for my engines?


Question from user bitmask at gaming.stackexchange.com.


Answer:

First, differentiate between intake air use/production, and intake air storage. It's a resource similar to electric energy or monopropellant. It's scooped by the intakes, stored in "tanks" provided by the intakes and drawn by engines from these "tanks". And since you're not supposed to be able to take a good supply of intake air to the orbit, the "tanks" provided are of puny size. Engine Nacelle can store 5 units of intake air, but it can scoop much, much more than that per second.


I can't give you a precise answer how to find out the rates, just - don't overthink it and don't worry. In most cases 1 intake (any) per engine is aplenty, 1 per 2 engines is sufficient. The primary practical difference is in aerodynamic properties, that is how much drag it causes - e.g. circular intakes are bad for supersonic flight. .


Thing is, the amount of intake air changes with atmospheric density, and that changes with altitude - exponentially (it also depends on airspeed and the intake area facing "into the wind" so if you mount your intakes backwards - or your plane turns tail-forward - you may face air starvation). At altitudes up to 20km you'll have to fail pretty hard to starve your engine of air. Above that - around 24-26km - there's an altitude threshold at which air becomes too thin and your engines are starved of air. Note the exponential nature of pressure makes the threshold hit hard; you can do very little about shifting it. You may push maybe a kilometer up through use of plenty intakes, but it's not really worth it (the extra drag from the added intakes will contribute more negatively than the extra flight altitude will benefit you).


There's a plenty of other "hidden" characteristics of the jet engine, like airspeed-thrust curve, pressure-thrust curve, etc. Goliaths are, for example, subsonic engines which really lose power at higher speeds, and won't allow for extreme altitudes either. And they have intakes big and efficient enough that it's very hard to starve them of air - you'll run out of thrust long before you reach altitude where their intakes can't keep up with the consumption. .


Answer from user SF. at gaming.stackexchange.com.



[BACK]

Does killing Diablo enemies quickly increase likelihood of better drops? Does killing Diablo enemies quickly increase likelihood of better drops?

Posted On: June 29, 2023
Title pretty much says it. I've unsuccesfully searched through Google and could not find any info. It definitely looks like the pace at which you kill an enemy (be it a mob, elite or a boss) af...[More]


How can I see the version of steam deck? How can I see the version of steam deck?

Posted On: May 18, 2023
I was thinking about buying a Steam Deck and to save a couple of bucks, figured I'd try to buy one used. Before I hand over the cash, I'd like to verify the one I'm buying is as advertised...[More]


What to know for first playthrough in Hogwarts Legacy? What to know for first playthrough in Hogwarts Legacy?

Posted On: August 18, 2023
Hey, just looking for some pointers that would help me for my first time playing - mostly what decisions have a later impact on gameplay, or quality of life tips :) no spoilers would be appreciated! T...[More]


Can you control what ore a drill harvests when its placed over multiple ores? Can you control what ore a drill harvests when its placed over multiple ores?

Posted On: January 5, 2024
I'm trying to harvest the maximum amount of uranium possible from a small patch. Unfortunately, there is a bordering coal patch nearby as well, and two of my electric mining drills are within rang...[More]


Villager breeder not working, showing angry particles: 1.17.1 Villager breeder not working, showing angry particles: 1.17.1

Posted On: June 15, 2023
I've built a villager breeder following this tutorial: . It worked for a while before it stopped working, as villagers show angry particles whenever they try to breed. I have broken and plac...[More]


Is there a limit for the waiting queue outside the vault? Is there a limit for the waiting queue outside the vault?

Posted On: December 13, 2023
Inspired by this question i wondered how many Dwellers can wait outside the vault. Even if there is no gameplay limit, what happens when more dwellers are waiting then can be graphically displayed bec...[More]


How do I give players already enchanted Tools - Armour - Weapons How do I give players already enchanted Tools - Armour - Weapons

Posted On: April 26, 2024
I'm making a map where I want players to be able to choose there kits/classes. The problem I'm having with it though is giving players already enchanted Tools/Armour/Weapons.I'm not sure if you can us...[More]


How to connect storage items with stills? How to connect storage items with stills?

Posted On: January 17, 2023
I'm pretty new to dwarf fortress, so sorry if this question doesn't make sense. I've been trying to use a still, but most of the options are unavailable because it needs an empty storage i...[More]


What is the highest speed possible? What is the highest speed possible?

Posted On: April 9, 2024
What is the maximum speed in MechWarrior Online? I know the light mechs easily go beyond 120 kph.Question from user Vanguard66 at gaming.stackexchange.com.Answer:Gauging by the Pirate's Bane Locust, w...[More]


Any way to fix Cathedral crash in Fallout 4? Any way to fix Cathedral crash in Fallout 4?

Posted On: March 24, 2023
I really searched it before on web. I can't get to the 3rd level in Cathedral (Master's Lair). All the solutions I found were from a very old thread in No Mutants Allowed. Nothing worked for m...[More]